> ## Documentation Index
> Fetch the complete documentation index at: https://clickhouse.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# function_* session settings

> ClickHouse session settings in the function_* generated group.

export const SettingsInfoBlock = ({type, default_value, changeable_without_restart}) => {
  return <div className="not-prose" style={{
    display: "flex",
    flexWrap: "wrap",
    alignItems: "baseline",
    columnGap: "0.5rem",
    rowGap: "0.125rem",
    margin: "0.375rem 0",
    fontSize: "0.8125rem",
    lineHeight: "1.125rem"
  }}>
      <div style={{
    fontWeight: 600,
    opacity: 0.72
  }}>Type</div>
      <div style={{
    overflowWrap: "anywhere"
  }}>{type}</div>
      <div style={{
    fontWeight: 600,
    opacity: 0.72,
    marginInlineStart: "0.5rem"
  }}>Default</div>
      <div style={{
    overflowWrap: "anywhere"
  }}>{default_value}</div>
      {changeable_without_restart && <div style={{
    fontWeight: 600,
    opacity: 0.72,
    marginInlineStart: "0.5rem"
  }}>
          Changeable without restart
        </div>}
      {changeable_without_restart && <div style={{
    overflowWrap: "anywhere"
  }}>
          {changeable_without_restart}
        </div>}
    </div>;
};

These settings are available in [system.settings](/docs/reference/system-tables/settings) and are autogenerated from [source](https://github.com/ClickHouse/ClickHouse/blob/master/src/Core/Settings.cpp).

<h2 id="function_base58_max_input_size">
  function\_base58\_max\_input\_size
</h2>

<SettingsInfoBlock type="UInt64" default_value="10000" />

<VersionHistory rows={[{"id": "row-1","items": [{"label": "26.6"},{"label": "10000"},{"label": "New setting that limits the input size of `base58Encode`, `base58Decode` and `tryBase58Decode` (whose conversion is quadratic in the input length) to 10 KB by default. The compatibility value `0` disables the limit, restoring the previous behavior of accepting arbitrarily large inputs."}]}]} />

Maximum size, in bytes, of a single input value for the functions `base58Encode`, `base58Decode` and `tryBase58Decode`. The generic `base58` conversion is quadratic in the input length, so a single large value can run for a very long time. `base58` is meant for short data (keys, hashes, addresses), so the default of 10 KB is a generous safety threshold. `base58Encode` and `base58Decode` throw `TOO_LARGE_STRING_SIZE` for larger inputs, while `tryBase58Decode` returns an empty string. A value of `0` disables the limit (the behavior before this setting was introduced). The linear `base32` and `base64` functions are unaffected.

<h2 id="function_date_trunc_return_type_behavior">
  function\_date\_trunc\_return\_type\_behavior
</h2>

<SettingsInfoBlock type="UInt64" default_value="0" />

<VersionHistory rows={[{"id": "row-1","items": [{"label": "25.7"},{"label": "0"},{"label": "Add new setting to preserve old behaviour of dateTrunc function"}]}, {"id": "row-2","items": [{"label": "25.4"},{"label": "0"},{"label": "Change the result type for dateTrunc function for DateTime64\/Date32 arguments to DateTime64\/Date32 regardless of time unit to get correct result for negative values"}]}]} />

Allows to change the behaviour of the result type of `dateTrunc` function.

Possible values:

* 0 - When the second argument is `DateTime64/Date32` the return type will be `DateTime64/Date32` regardless of the time unit in the first argument.
* 1 - For `Date32` the result is always `Date`. For `DateTime64` the result is `DateTime` for time units `second` and higher.

<h2 id="function_implementation">
  function\_implementation
</h2>

Choose function implementation for specific target or variant (experimental). If empty enable all of them.

<h2 id="function_locate_has_mysql_compatible_argument_order">
  function\_locate\_has\_mysql\_compatible\_argument\_order
</h2>

<SettingsInfoBlock type="Bool" default_value="1" />

<VersionHistory rows={[{"id": "row-1","items": [{"label": "24.3"},{"label": "1"},{"label": "Increase compatibility with MySQL's locate function."}]}]} />

Controls the order of arguments in function [locate](/docs/reference/functions/regular-functions/string-search-functions#locate).

Possible values:

* 0 — Function `locate` accepts arguments `(haystack, needle[, start_pos])`.
* 1 — Function `locate` accepts arguments `(needle, haystack, [, start_pos])` (MySQL-compatible behavior)

<h2 id="function_range_max_elements_in_block">
  function\_range\_max\_elements\_in\_block
</h2>

<SettingsInfoBlock type="UInt64" default_value="500000000" />

Sets the safety threshold for data volume generated by function [range](/docs/reference/functions/regular-functions/array-functions#range). Defines the maximum number of values generated by function per block of data (sum of array sizes for every row in a block).

Possible values:

* Positive integer.

**See Also**

* [`max_block_size`](/docs/reference/settings/session-settings/max#max_block_size)
* [`min_insert_block_size_rows`](/docs/reference/settings/session-settings/min-insert#min_insert_block_size_rows)

<h2 id="function_sleep_max_microseconds_per_block">
  function\_sleep\_max\_microseconds\_per\_block
</h2>

<SettingsInfoBlock type="UInt64" default_value="3000000" />

<VersionHistory rows={[{"id": "row-1","items": [{"label": "23.7"},{"label": "3000000"},{"label": "In previous versions, the maximum sleep time of 3 seconds was applied only for `sleep`, but not for `sleepEachRow` function. In the new version, we introduce this setting. If you set compatibility with the previous versions, we will disable the limit altogether."}]}]} />

Maximum number of microseconds the function `sleep` is allowed to sleep for each block. If a user called it with a larger value, it throws an exception. It is a safety threshold.

<h2 id="function_visible_width_behavior">
  function\_visible\_width\_behavior
</h2>

<SettingsInfoBlock type="UInt64" default_value="1" />

<VersionHistory rows={[{"id": "row-1","items": [{"label": "24.1"},{"label": "1"},{"label": "We changed the default behavior of `visibleWidth` to be more precise"}]}]} />

The version of `visibleWidth` behavior. 0 - only count the number of code points; 1 - correctly count zero-width and combining characters, count full-width characters as two, estimate the tab width, count delete characters.